Alloy for permanent magnets



Patented Apr. 25, 1944 2,347,543 ALLOY FOR PERMANENT MAGNETS WalterSiemensstadt, Property Custodian Dannohl and Hans Neumann, Berlin-Germany; vested in the Alien No Drawing. Application October 27, 1937,Serial No. 171,214. In Germany January 7, 1937 Claims.

Our invention relates to an alloy for permanent magnets.

It is known to employ as material for the manufacture of permanentmagnets alloys of cobalt, nickel and copper and alloys of irons, nickeland copper. The just-mentioned magnets of cobalt, nickel and copper aredescribed in our U. S. Patent No. 2,170,047, granted August 22, 1939, onour copending application Serial No. 111,252, filed November 1'7, 1936,of which this is a continuation-in-part. These magnets have excellentmagnetic qualities such as a potential coercive force above 100 oerstedtogether with the advantage of being machineable by cutting tools andhaving a higher mechanical strength than other high grade magnets.

According to the present invention, similar advantages are obtained byemploying alloys of cobalt, nickel, copper and iron for producingpermanent magnets. Magnets of this composition have considerably bettermagnetic properties than the known iron-nickel-copper alloys, and areadvantageous even in comparison with ternary nickel-cobalt-copperalloys, since by virtue of the iron content they may have a cheapercomposition and also present improved working properties.

v Magnets according to our present invention contain 1 to 35% iron, to45% nickel, 1 to 70% cobalt, and to 80% copper.

Alloys containing 5 to iron, 15 to nickel, 5 to cobalt and 30 to 60%copper show especially favorable magnetic properties. The magneticproperties of magnets according to the invention are further enhan ed ifthe alloys are first heated above 1000 C.,"

500 and 750 C.

The improvement of the magnetic properties attained by alloys accordingto the invention will become apparent from the following table referringto a number of examples of different composition.

In the first column or this table are indicated then quenched andfinally reheated to a temperature between the alloys of which thosedesignated by a refer to iron-nickel-copper, whereas the alloys band 0are obtained from the alloys a by substituting cobalt for a portion ofiron. The last three columns of the table indicate the values of theremanence, the coercive force and the magnetic power Br.JHc Particularlynoteworthy is the great increase of the coercive force present in everycase. Thus, for instance, with an alloy containing 40% iron, 20% nickeland 40% copper, the coercive force increases from 30 to 240 oersted ifcobalt is substituted for 30% iron. At the same time also the remanenceincreases by 10% from 5,100 to 5,600 gauss. The improvement is alsoapparent from the increase in the magnetic power Bib-7H0 from 1.5.10 to12.6.10.

In some cases, such as in examples 1b and 2b, the substitution of cobaltfor iron effects not only an increase in the coercive force, but also anincrease in the remanence. In other cases, such as in alloy 5b,the-remanence is not affected, and in some cases a decrease of theremanence is noticeable, as will be seen from alloys 4b and 6!: showinga 'decrease of approximately 10%. In the last-mentioned case, thecoercive force is considerably increased so that the product of thesetwo magnitudes shows a considerable improvement of the magneticproperties as compared to the known iron-nickel-copper alloys.

The alloys designated by a were produced with the most favorable heattreatment in order to attain the best possible magnetic properties. Thealloys designated by b and 0 were produced in such a manner that thematerial was at first heated for 10 hours at a temperature of 1,050 and1,100 centigrade respectively, then quenched in oil, annealed for 1 to40 hours at a temperature of 600 to 700 centigrade and finally cooleddown to room temperature. The fluctuations in the annealing period arefound necessary, since different compositions required different periodsfor obtaining the best magnetical properties. For other compositionsthan given in the table, departures from these periods and temperaturesmay appear appropriate.

The alloys may contain small amounts of reducing materials, forinstance, about 1% man- 'ganese, small quantities of silicon, magnesium,

aluminum or beryllium, or several of such common additions.

What is claimed is:

1. A permanent magnet formed of an alloy containing 5 to 25% iron, 15 to35% nickel, 5 to 40% cobalt, and a balance consisting substantially of30 to 60% copper, besides minor amounts of customary additions andimpurities, and being magnetized up to a coercive force above oerstedand a remanence above 1,000 gauss;

2. A permanent magnet formed of an alloy and being magnetized to amagnetic power above 10.

5. A permanent magnet formed of an alloy containing 1 to iron,

10 to nickel, 5 to cobalt and a balance of 20 to consistingsubstantially of copper, and exhibiting a magnetic power above 10 uponquenching from above 1000 C. and tempering between 500 and WALTER.DANN6HL. HANS NEUMANN.

